1. Field of the Invention
The present invention relates to a process for producing a self-supporting package having an outlet stopper which is used for containing fluid materials, and an apparatus for producing said package. More particularly, the present invention relates to a process for producing a self-supporting package which comprises holding a self-supporting bag having a sealing layer made of a thermoplastic resin on the inner side at a vertical position, filling contents after opening an opening part of the self-supporting bag, supplying an outlet stopper made of a thermoplastic resin to the opening part, and sealing the outlet stopper and the opening part together, and an apparatus for producing said package. The present invention relates to the process and the apparatus having such advantages that the self-supporting bag can be filled with contents at a high speed, that excellent sealing can be realized in a short time by sealing the layer on the self-supporting bag and the outlet stopper together by the ultrasonic vibration, and that the sealing can be surely achieved even when foreign substances are present on the face of sealing.
2. Description of the Related Art
Commercial products which have heretofore been sold in bottles of glass or hard plastics, such as milk, soy sauce, oil, cosmetics and other like products of a fluid or slurry form, are recently sold in packages of paper cartons, bottles of thin plastic sheets, and bags of plastic films (pouches).
An outlet stopper is attached to paper cartons and thin plastic bottles. A necessary amount of the content is taken out each time from the package through the outlet stopper and the remaining amount is kept in the package by closing the outlet stopper. Pouches having an outlet stopper are also used. Pouches having the self-supporting property which can stand self-supported on a table in the condition filled with contents are produced for realizing still easier handling in use.
As the self-supporting package having an outlet stopper, a package having an opening part at the top is preferred. Self-supporting packages having an opening part at the top, such as those shown in FIG. 1 [Japanese Utility Model Application Laid-Open No. Showa 60(1985)-139754] and in FIG. 2 [Japanese Utility Model Application Laid-Open No. Showa 63(1988)-76653], are currently produced. However, the self-supporting packages shown in FIGS. 1 and 2 have drawbacks in that bulkiness of the main part 1 of the outlet stopper causes a problem in the process of supplying the self-supporting bag, and that speed of filling contents from the inlet-outlet 2 of the main part of the outlet stopper 1 is very low because the inlet-outlet is generally small and increase in the productivity is difficult. For increasing the productivity by increasing the speed of filling, a method in which a large open part 4 is formed in addition to the outlet stopper 3 as shown in FIGS. 3 and 4, and the large open part is closed by heat sealing after the package is filled with contents, has been adopted. However, this method has drawbacks in that bulkiness of the outlet stopper makes a problem in the process of supplying the self-supporting bag and that the outlet stopper cannot be formed at the central top of the self-supporting package and the shape of the package is limited.
As the method of sealing or adhering a packaging bag having a sealing layer of a thermoplastic resin to an outlet stopper made of a thermoplastic resin, a method of heat sealing, a method of using an adhesive, and a method of sealing with high frequency dielectric heating or dielectric heating, have heretofore been known.
Among these methods, the method of using an adhesive has drawbacks in that time and care are required, that a long time is necessary for curing, that smell remains after the adhesion, and that many types of adhesive cannot be used depending on contents, and this method is not practically used. The method of sealing with high frequency dielectric heating has drawbacks in that thermoplastic resins generating heat with high frequency dielectric heating are limited to resins having a large dielectric loss such as polyvinyl chloride and polyvinylidene chloride, and that a special method, such as mixing metal powder into the thermoplastic resin to be heated or burying pieces of metal in a packaging bag or an outlet stopper, must be used because the high frequency dielectric heating is conducted by making use of ohm loss caused by the vortex current induced in the material to be heated which is a conductive material like a metal. Therefore, application of this method is naturally very limited. The method of heat sealing is conducted by heating a packaging bag and an outlet stopper with a heating plate from the outside of the packaging bag while they are pressed together. The principle of the heat sealing is to make use of heat transfer and simple. The heat sealing can be surely performed by using a suitable condition so long as the material of the sealing layer at the inner face of the packaging bag and the material of the outlet stopper are the same. Therefore, the method of heat sealing is generally used.
Recently, sealing methods of an outlet stopper using ultrasonic vibration have been proposed. An example of such method was disclosed in Japanese Utility Model Application Laid-Open No. Showa 60(1985)-187032. In the disclosed method, an outlet stopper like a round stopper having a cylindrical sealing face is sealed by the ultrasonic vibration to a plastic film before the plastic film is processed to the form of a bag, and then a packaging bag is prepared from the plastic film having the outlet stopper. This method of preparation of a bag inevitably requires that the packaging bag has a shape in which the outlet stopper is attached to the front side part or the back side part. The outlet stopper at the side part disturbs the operation of filling contents in the process that follows. This causes difficulty for automation and also requires a complicated process to seal the open part again. Therefore, the disclosed method is inferior as an industrial process with respect to workability as well as to productivity.
A method of heat sealing a packaging bag and an outlet stopper together which has heretofore been used widely is described in the following with reference to FIGS. 5, 6 and 7. FIG. 5 show the whole part of an outlet stopper 3. The outlet stopper is composed of the main part 1 and a cap 5. Closing and opening of the main part 1 with the cap 5 are made by using a screw formed on each of the main part 1 and the cap 5. The main part 1 is made of a thermoplastic resin and generally produced by a molding method, such as injection molding. As the shape of the sealing part 6 of the outlet stopper, a shape such as that of the ship-shaped flange 7 shown in the figure is preferable because a large area can be obtained for sealing with the packaging bag. One to several ribs 8 for sealing may be formed on the sealing face of the ship-shaped flange 7. The cap 5 is made of a synthetic resin such as a thermoplastic resin or a metal such as aluminum. Material of the cap is not limited so long as the cap 5 and the main part 1 of the outlet stopper can be screwed into each other and closed together tightly.
FIG. 6(A) shows a packaging bag 9 in the condition before the main part 1 of the outlet stopper is inserted into the opening part 4 at the top of the bag. FIG. 6(B) shows the packaging bag in the condition after the main part 1 of the outlet stopper is inserted into the opening part 4 and sealed to the bag. Before the outlet stopper 3 is sealed, the packaging bag 9 has the shape of so called three side sealed bag in which the bottom part and both side parts have been sealed with a suitable method such as heat sealing. The material film of the packaging bag generally has a single layer structure or a multi-layer structure having two or more layers made of thermoplastic resins. As material of the innermost layer, a material of the same type as that of the sealing part 6 of the main part 1 of the outlet stopper is generally used to assure strength of the sealing. When the sealing of the outlet stopper to the packaging bag 9 is made after the packaging bag 9 is filled with contents, the main part 1 of the outlet stopper is generally sealed to the packaging bag while the cap 5 is screwed into the main part 1 of the outlet stopper. When the sealing is made before the bag 9 is filled with contents, the main part 1 of the outlet stopper is generally sealed to the packaging bag while the cap 5 is taken off from the main part 1 of the outlet stopper, and the cap 5 is screwed into the main part 1 of the outlet stopper after the bag is filled with contents from the inlet-outlet 2.
FIG. 7 shows a perspective view illustrating the sealing process of an outlet stopper by heat sealing when the outlet stopper 3 is inserted into the packaging bag 9 by a suitable method, placed at a specified position and sealed to the packaging bag. Ends of the sealing plate 10 and the sealing plate 11, which are arranged at the positions facing to each other, have each a shape corresponding to that of the sealing part 6 of the ship-shaped flange 7 of the outlet stopper which is shown in FIG. 5, and also have each straight side parts 12 which are straightly extended sideward from the shape corresponding to that of sealing part 6 so that the side parts of the packaging bag shown in FIG. 6 can be sealed simultaneously.
Sealing plates 10 and 11 are each connected to heating plates 13 and 14 by forming into a single body or by using bolts. The sealing plates 10 and 11 and the heating plates 13 and 14 are made of a metal such as aluminum, stainless steel, and steel. The heating plates have each a heating device such as a cartridge heater buried in it or a heater plate attached to the surface, and a temperature sensor to control the heating plate at a temperature suitable for heat sealing.
The heating plates 13 and 14 move away from or to each other to open or close the heating plates, respectively, as shown by the arrows in the figure. After the outlet stopper 3 is inserted into the packaging bag 9, the heating plates 13 and 14 move to each other to close the plates when center of the outlet stopper 3 inserted into the packaging bag 9 reaches the position at the center of the sealing plates 10 and 11 which are arranged at positions facing to each other. The sealing layer which is the innermost layer of the packaging bag 9 and the ship-shaped flange 7 are heated and sealed to each other by pressing the heating plates 13 and 14 to the ship-shaped flange of the main part 1 of the outlet stopper for a specified time at a suitable pressure. Then, the heating plates 13 and 14 move away from each other to open them. By repeating this operation twice or more, a strong sealing can be achieved.
The heating plates 13 and 14 are driven by a suitable mechanism such as an air cylinder, an oil pressure cylinder, and mechanical cam driving. Time necessary for one sealing is 1 to 3 seconds, 1.5 seconds in general, although the time is different depending on material and thickness of the packaging bag 9, material of the ship-shaped flange 7 of the main part 1 of the outlet stopper, area for the sealing, and pressure for the sealing. Because sufficient sealing strength cannot be obtained by one sealing operation alone, the sealing operation is repeated 2 to 3 times. Furthermore, a process for cooling the sealed part is required to cool the sealed part quickly and prevent detachment of the sealed part. Therefore, increase in the productivity is limited by these factors. Particularly, when a bag is filled with contents through the outlet-inlet 2 of the main part 1 of the outlet stopper shown in FIG. 6 after the outlet stopper 1 is sealed to the packaging bag 9, the time required for filling the packaging bag with the contents, in other words the filling speed, is decreased to a large extent because the outlet-inlet is small. Therefore, increase in the productivity is further difficult.
When the packaging bag is filled with contents while the opening part 4 in the packaging bag 9 is open, in other words, when the packaging bag is filled with contents at a high speed while a large opening is made in the packaging bag before the outlet stopper is attached to the packaging bag and then the outlet stopper 3 is sealed to the bag, problems such as those described in the following arise. When the contents are fluid, the fluid contents tend to adhere to the sealing face of the packaging bag 9. The adhered fluid works as a foreign substance and is vaporized by the heat of the sealing. This causes formation of bubbles on the sealed part and formation of so called blisters. When these phenomena occur to a large extent, defect sealing such as a broken bag at the sealed part frequently takes place. When solid contents adhere to the sealing part, such a trouble that the sealing cannot be made at all arises and reliability of the sealing to keep the contents is all lost. Particularly, when the content is a food, germs invade into the package through the defect sealed part to cause rot by the contamination with the germs. When the content is a drug which requires the sterile condition, the worst result of contamination with germs arises.